Composite magnesium-titanium conductor

ABSTRACT

Magnesium base alloy containing at least about 0.05 weight per cent lithium with a titanium overcoating suitable for use as an electrical conductor.

United States Patent Kuchek Aug. 19, 1975 COMPOSITE MAGNESIUM-TITANIUM 3,189,441 6/1965 Frost 1 75/166 R 3,189,442 6/1965 Fl'OSt 75/168 R 3,320,661 5/1967 Manko 29/197 [75] Inventor; Henry A. Kuchek, Auburn, Mlch. 3,333,956 8/1967 Foerster 75/168 R 3,671,415 6/1972 King 204/286 X [73] Ass1gnee: The Dow Chemical Company, 4 4 B 2 Midland Mich 3,80 ,739 /1974 ergeron 04/266 [22], Filed Aug 1 197 4 FOREIGN PATENTS OR APPLICATIONS 448,830 5/1944 Canada 174/126 CP pp Q: 493,810 1,045,966 10/1966 United Kingdom 174/126 01 Related U.S. Application Data Division of Ser. No. 402,563, Oct. 1, 1973, Pat. No. 3,849,879.

References Cited UNITED STATES PATENTS 9/1964 Foerster 75/168 R Primary ExaminerW. Stallard Assistant Examiner-Arthur J. Steiner Attorney, Agent, or FirmRobert W. Selby 57 ABSTRACT Magnesium base alloy containing at least about 0.05 weight per cent lithium with a titanium overcoating suitable for use as an electrical conductor.

11 Claims, No Drawings COMPOSITE MAGNESIUM-TITANIUM CONDUCTOR' Cross-Reference to Related Application This is a division of application Ser. No. 402,563 filed Oct. 1, 1973, now U.S. Pat. No. 3,849,879.

BACKGROUND OF THE INVENTION This invention pertains to an electrical conductor and more in particular to a titanium clad magnesium conductor.

It is oftentimes desirable to have an electrical conductor resistant to a corrosive environment Electrical conductors with a casing of iron, titanium or tantalum and a core of aluminum,- copper, sodium, tin or zinc, and methods of making such conductors are described in U.S. Pat. Nos. 3,671,415 and 3,717,929, and British Patents l,045,966 and 1,227,506. It is desired to pro- 'vide an electrical conductor resistant to the detrimental corrosive effects of, for example, caustic environments.

SUMMARY OF THE INVENTION A novel electrical conductor suitable for use in corrosive environments and a method of forming such conductor have surprisingly been developed. The method comprises at least partially filling a hollow titanium body with a molten magnesium base alloy containing at least about 0.05 weight per cent lithium by first introducing the molten alloy into the titanium body and then solidifying the molten alloy. The magnesium alloy contacts the inner surface of the titanium body sufficiently to maintain electrical contact between the core and cladding during use. Herein, the term titanium includes pure titanium and titanium base alloys.

The magnesium alloy cored-titanium cladded composite is especially suited for use as an electrical conductor in corrosive environments such as those containing a high concentration of an alkali as sodium hydroxide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The titanium cladded-magnesium alloy composite of the present invention is formed by first melting either alloyed or preferably pure magnesium metal and further alloying the molten metal with about 0.05 to about weight per cent and preferably from about 0.1 to

about 5 weight per cent and even more preferably from about 0.1 to about 0.5 weight per cent lithium or melting a pre-alloyed magnesium-lithium alloy and heating the molten metal to a temperature less than that at which substantial loss of magnesium and/or lithium occurs. Preferably the metal is heated to within a temperature range of from about 1250F. to about 1400F. and preferably about 1275F. to about 1325F. A hollow titanium body, such as a rectangular or circular cylinder pipe or tube, is at least partially and preferably substantially entirely filled with the molten magnesiumlithium alloy. Such filling can be carried out by, for example, pouring the molten metal into the titanium tube. However, it is preferred to employ a titanium tube having one end thereof sealed by, for example, welding and immersing at least the open end of the tube in the molten magnesium-lithium alloy. By means as generally described in U.S. Pat. No. 3,364,976, gases within the tube react with the molten magnesium to thereby cause filling of the tube with the molten metal.

The surface of the titanium in contact with the molten magnesium is generally cleaned to remove at least any excess grease and oil present. Preferably substantially all of the organic contaminants are removed by well known means prior to filling or casting the titanium tube with the molten magnesium. The inner surface of the tube can be further cleaned by known mechanical or chemical means to remove surface oxide before casting.

It has been surprisingly found that the use of an effective amount of lithium in a magnesium alloy enhances the electrical contact between the titanium overcoating or cladding and the magnesium alloy to thereby form a composite having both satisfactory physical properties and electrical conductivity for use as an electrical conductor in, for example, chlorine and sodium hydroxide producing electrolytic cells. The composite of the present invention is also suitable for use as a substrate for a dimensionally stable electrode in, for example, chloralkali electrolytic cells.

The metals described herein are preferably the pure metals containing the impurities normally associated with the commercially obtainable metals. Preferably the magnesium-lithium core alloy has a composition consisting essentially of at least about weight per cent and preferably at least about 99 weight per cent magnesium together with lithium within the above de-. scribed composition ranges.

The following examples further illustrate the invention.

EXAMPLES l-l 3 Magnesium with a minimum purity of 99.80 weight per cent was melted in an appropriate container and heated to 1300F. A standard flux cover was used to minimize oxidation of the magnesium. Sufficient metallic lithium was added to and mixed with the molten magnesium to form magnesium base alloys containing 0.05, 0.1, 0.5 or 5 weight per cent lithium. The Mg-Li alloys were maintained at a temperature of 1300F.

Commercially pure titanium tubes with an outside diameter of one-half inch, a wall thickness of 0.02 inch and one end welded closed were cleaned by washing with acetone. The cleaned tubes were then immersed (open end downwardly positioned) in a bath of the molten Mg-Li alloy for 5, 10 or 30 minute periods to substantially entirely fill the tubes with the Mg-Li alloy.

The alloy filled tubes were slowly removed from the molten alloy bath to solidify the Mg-Li alloy within the titanium tubes to thereby form titanium clad-Mg-Li alloy composites.

The voltage dropacross a 6 inch length of the composite was determined at room temperature by electrically connecting a 15 ampere source to each composite and measuring the voltage drop by standard means. Table I contains data obtained during the above de scribed tests. This data confirms that the titanium clad- Mg -Li alloy composite has a low voltage decrease over a unit length and is suitable as an electrical conductor.

TABLE 1 Time tube in molten metal (minutes) Example Li(Wt.%) Voltage drop in 6 inch length (millivolts) EXAMPLES 14 AND 15 COMPARATIVE EXAMPLES A AND B Two titanium tubes were filled with 99.8 weight per cent pure magnesium substantially as described for Examples 1-13. The voltage drop across a 6 inch length of the solidified titanium-Mg composite was determined (as in Examples 1-13) to be 18 and 1.1 millivolts. Examples A and B confirm that consistently low voltage drops were not obtained with composites using pure magnesium as a core material.

Composites with a titanium alloy cladding and a magnesium-1O weight per cent lithium alloy core with acceptable properties are produced in accord with the procedure of Examples 1-13. In a manner as described for Examples 1:13 composites with acceptable proper- ,ties? are produced using molten metal temperatures of 125W. and 1400 7 What is claimed is: l. A composite comprising an in situ cast core consisting essentially of about 0.05 to about 10 weight per cent lithium and the balance magnesium with a titanium cladding.

2. A composite comprising an in situ cast core consisting essentially of about 0.05 to about 10 weight per cent lithium and the balance magnesium with a cladding consisting essentially of titanium, the composite adapted for use as an electrical conductor in corrosive alkali containing environments.

3. The composite of claim 1 wherein the core contains about 0.1 to about 5 weight per cent lithium.

4. The composite of claim 2 wherein the core contains about 0.1 to about 5 weight per cent lithium.

5. The composite of claim 1 wherein the core contains about 0.1 to about 0.5 weight percent lithium.

6. The composite of claim 5 wherein the magnesium base alloy contains at least about 99 weight percent magnesium.

7. The composite of claim 5 wherein the titanium cladding is cylindrical in shape.

8. The composite of claim 1 wherein the magnesium base alloy contains at least about weight percent magnesium.

9. The composite of claim 2 wherein the core contains about 0.1 to about 0.5 weight percent lithium.

10. The composite of claim 9 wherein the magnesium base alloy contains at least about 99 weight percent magnesium.

11. The composite of claim 3 wherein the cladding is cylindrical in shape.

titanium 

1. A COMPOSITE COMPRISING AN IN SITU CAST CORE CONSISTING ESSENTIALLY OF ABOUT 0.05 TO ABOUT 10 WEIGHT PER CENT LITHIUM AND THE BALANCE MAGNESIUM WITH A TITANIUM CLADDING.
 2. A composite comprising an in situ cast core consisting essentially of about 0.05 to about 10 weight per cent lithium and the balance magnesium with a cladding consisting essentially of titanium, the composite adapted for use as an electrical conductor in corrosive alkali containing environments.
 3. The composite of claim 1 wherein the core contains about 0.1 to about 5 weight per cent lithium.
 4. The composite of claim 2 wherein the core contains about 0.1 to about 5 weight per cent lithium.
 5. The composite of claim 1 wherein the core contains about 0.1 to about 0.5 weight percent lithium.
 6. The composite of claim 5 wherein the magnesium base alloy contains at least about 99 weight percent magnesium.
 7. The composite of claim 5 wherein the titanium cladding is cylindrical in shape.
 8. The composite of claim 1 wherein the magnesium base alloy contains at least about 90 weight percent magnesium.
 9. The composite of claim 2 wherein the core contains about 0.1 to about 0.5 weight percent lithium.
 10. The composite of claim 9 wherein the magnesium base alloy contains at least about 99 weight percent magnesium.
 11. The composite of claim 3 wherein the titanium cladding is cylindrical in shape. 